Rectifying tube



Nov. 4, 1930. 4 R 1,780,504

RECTIFYING TUBE Filed Aug. 1, 1927 INVENTOR Jam/2a fi/bler ATTORNEYPatented Nov. 4, 193G UNlTED STATES PATENT UFFHE JACQUES RISLER, OFPARIS, FRANCE, ASSIGNOR TO RISLER CORPORATION OF AMERICA, OF KANSASCITY, MISSOURI, A CORPORATION OF DELAWARE RECTIFYING TUBE Applicationfiled August 1, 1927, Serial No. 209,788, and in France June 3, 1927.

My invention relates to vacuum tubes for rectifying alternating current,and more particularly to tubes with electrodes of unequal sizes orshapes.

It is already known that when an electric current of suitable strengthis passed through a vacuum tube having two electrodes of very unequalsize the smaller electrode will become hot while the larger electroderemains relatively cool. In such a state the tube acts as a thermionicvalve with the smaller electrode as cathode. A serious drawback to thepractical employment of such tubes is the adsorption of gas by the metalof, and from, the hot cathode. This adsorption reduces the pressure ofgas in the tube and causes the resistance of the tube to rapidlyincrease with use.

The object of the present invention is to obviate this difficulty andfurnish a rectifying tube whose resistance remains approximatelyconstant over a long period of use.

My invention comprises a vacuum tube with one or more cathodes of such ashape that they can be hollowed out, the hollows containing a substancewhich liberates a gas on heating. In use the cathodes become hot andcause gas to be liberated from the material contained within them, thisevolved gas escaping to the 'main body of the tube through a suitableopening or openings in the walls of the cathodes. The gas so liberatedolf-sets the effect of the adsorption of gas by the metal of thecathode.

One form of my invention is represented diagrammatically in theaccompanying drawing. This form is a double cathode tube suitable forrectifying both halves of the alternating current cycle.

The glass bulb, 1, is an ordinary lamp bulb. The cathodes, 2, arecylindrical in form and bored through the center with holes, 3, whichcontain the material that liberates as on heating. Near the top theelectro es, 2, are perforated with, holes, 4, through which the gasliberated from the material in the holes, 3, may esca e into thebulb, 1. The anode, 5, has a sur ace relatively much greater than thatof the cathodes, 2.

The relative sizes of the cathodes 2 and the anode, 5, may be variedwidely. Also the distance between the ends of the cathodes, 2, and theanode, 5, may be varied. For a tube which will carry forty tosixtymilliamperes the cathodes may suitably have an outside diameter ofabout 0.5 mm. and a length of 2 to 3 cm. The anode would then suitablyhave an exposed area of about 4: 0111 For such a tube the distancebetween the ends of the cathodes and the anode surface may be 2 to 4 mm.

The anode, 5, may be of any stable metal; soft iron is suitable. Thecathodes, 2, should preferably be made of some high melting conductorsuch as platinum or tungsten.

A variety of materials may be used in the holes, 3. Particularlysuitable are salts of the alkaline earths and carbon compounds, such asanthra'quinone, which have very low vapor pressures. lVhen salts of thealkaline earths are used they should preferably be finely divided.

Any stable gas may be used within the bulb. Its pressure should be suchthat the tube has as little resistance to the current as possible, andwill, therefore, lie usually between 2 and 10- mm. of mercury.

What I claim and desire to secure by Letters Patent is:

A rectifying tube comprising a bulb evacuated to 2 to 10' mm. containingan anode with an exposed surface of substantially 4 cm, and two hollowperforated cathodes each substantially 0.5 mm. in diameter and 2 cm.long and placed with their ends 2 to 4 mm. from the anode surface, thehollows in the cathodes containing an alkaline earth salt.

In testimony whereof I aflix m si nature.

JACQUES is'inn.

dill

